Vehicles which use human generated power have been around for centuries. The advantages of energy storage in these vehicles has been well known for over a century. For example, U.S. Pat. No. 89,882, issued to S. Wilmarth, dated May 4, 1869, discloses the use of a flywheel to improve the performance of a three-wheeled, human-powered velocipede. Likewise, U.S. Pat. No. 190,353, issued to W. S. Mitchell on May 1, 1877 discloses a spring as an alternative form of energy storage; again, to improve the performance of a velocipede.
The typical pedal mechanism used on most bicycles, using chains and sprockets, inputs power in a cyclical fashion, with maximum input only when the pedal is horizontal. In addition, the aforementioned pedal mechanism requires numerous different sprockets, changed via a shifting mechanism, to be able to change gears, depending on the terrain. People have understood the limitations of the typical pedaling system used on most bicycles for many years. Some have tried to make various elliptical sprockets to try to extend the portion of a rotation where the maximum power input is obtained; that is during the horizontal position of the pedals. There has been some improvement in performance using this technique; yet, because of the complexities of "un-round" sprockets, and the need for special chain-handling techniques to deal with it, this method has never been wide spread. This problem is exacerbated by the fact that ten to twenty ratios are still required to meet the needs of running on various terrains. As with most other bicycles built today, they utilize a shifting mechanism with a "derailleur" system to meet those requirements.
More recently, U.S. Pat. No. 5,035,678 issued to M. D. Hageman discloses an "Energy-Storing Bicycle Sprocket Drive System". This device helps to improve the efficiency of a chain and sprocket type bicycle drive system by using a set of springs to add torque to the point of minimum applied leverage. However, it would be advantageous to have a vehicle that is not constrained by the requirements of using chains, sprockets, idlers, derailleurs, etc., with their associated penalties of added weight, maintenance, and safety concerns.
Over much of the last century, many people have also worked to change the position that a bicycle rider sits while pedaling. For instances, they are many "recumbents" on the market today. These recumbents let the rider sit in a reclining riding position; rather than the more common upright position used for most bicycles. This configuration gives a much lower wind resistance; and, to most riders, a more comfortable riding position. While offering certain advantages, the recumbents still have the same limitations of requiring the use of multiple sprockets and the associated gear changing mechanism. In addition, they have even longer chains; which adds both weight and complexity to the recumbents.
Most bicycle racers now have the rider's feet tied to the pedals so that they can pull up on one pedal, as they push on the other. This technique also lets one add energy during the minimum energy portion of a cycle, i.e., at the two vertical positions of the pedal stroke. This has helped to increase overall mechanical efficiency of human-power. Yet, at the same time, because the rider's feet are indeed tied to the pedals, it also adds a level of danger; especially, during slow speed operating and when stopping.
Similar efforts have been made with regard to watercraft. Since the mid-1980's, people have experimented with hydrofoils on human-powered watercrafts. For example, Allan V. Abbott, riding such a craft, called the "Flying Fish II", recorded a record speed of 6 minutes, 39.44 seconds over a 2,000 meter course. This was about 10 seconds faster than the single-person rowing-shell record (reference December 1986"Scientific American"). This craft, as well as other hydrofoil human-powered boat (hereinafter referred to "human powered boats"), exhibited several problems which limited their use to extremely well-conditioned athletes. First, the amount of power required to get the hydrofoil human-powered boat up on plane took about 1.5 HP for about 3 seconds. This level of power takes a very well-conditioned athlete to produce, even for that short period of time. Second, because of the cyclical motion of the bicycle type power-transmission, there were losses in the thrust from the propeller. The above mentioned Abbott estimated this loss to be from 2% to 5% of the total. Third, the stability of the hydrofoil was quite poor.
Since the turn of the 20.sup.th century, people have also tried to develop aircraft to accomplish human-powered flight. During the late 1970's and early 1980's, several very successful human-powered airplanes were demonstrated. This included the "Gossamer Condor", the "Gossamer Albatross", and the "Monarch B", each winning various "Kramer awards" (prizes set up by Henry Kramer, a British industrialist; reference November 1985"Scientific American"). All of these crafts exhibited similar problems to the aforementioned hydrofoils and human powered boats.
The "Monarch B" was successful with one problem: that of energy storage. This craft utilized a separate electric generator with a number of NiCd batteries for energy storage, along with an electric motor that drives a huge propeller, in parallel to the chain and sprocket system that drives that propeller. This composite drive system did the job to win the Kramer Prize; yet, again, required an extremely well-conditioned athlete to accomplish this feat.
By utilizing the present invention, all of the aforementioned limitations can be eliminated. Only wires (which can be quite flexible and easily routed) are required to transmit power from the generator to the energy storage device; and then from the energy storage device to the output motor (or in the case of human powered boats, two motors are used in the preferred embodiment). Thus, the rider can be in sitting in the most effective position (which may vary from person to person). In addition, the frame of the vehicle (whether using two, three, or four wheels, on a wheeled vehicle) can be designated with a maximum strength to weight ratio, while minimizing wind resistance and maximizing overall efficiency, without being constrained by the placement of chains, multiple sprockets, and complex derailleur systems.
The use of harmonic drives to get efficient, high gear increasing ratios has been well known for decades. For instance, a leading supplier of harmonic drives has informed the inventor that harmonic drives have been used by the United States military for hand driven electric generators for use with radio communications since the 1960's. However, by using highly efficient, switched reluctance, or rare earth magnet generators, coupled with the profiling disclosed later in this document, as part of this invention, the overall efficiency of such a device would be significantly improved. For at least a decade, the high efficiencies of such switched reluctance motors and generators have been well known. For instance, the motors used to drive the feed roll on rotary plotters have used switched reluctance motors to drive such feed rollers. Since such feed rollers are typically made of plastic, and thus have no good way to dissipate the heat from the motors, they typically require motors with efficiencies greater than ninety-six percent (96%), to minimize the heat build-up in the first place. The switched reluctance motors proved to be extremely reliable in these applications, largely due to their high efficiencies. Likewise, as disclosed in the September 1998 issue of Aerospace Engineering, because of their high efficiencies, switched reluctance motors and generators are effectively used in the direct drive motors and generators that are part of a gas turbine integrated power unit used in military aircraft. In addition, since the early 1990's, rare earth magnets (e.g., the neodimium) motors have been commercially available with efficiencies in excess of ninety-six percent (96%). These motors are now used in numerous industrial applications where performance is the major criteria, largely in brushless servo drives. Again, as with the switched reluctance motors, the major requirements were for high performance and reliability, which mandated high efficiencies to eliminate the need for large cooling fans and heat sinks, previously required by similar applications when using less efficient motors.
By significantly increasing the overall efficiency of the drive system and energy storage device, the present invention enables an "average" human to accomplish similar feats as the above-mentioned Monarch B and Flying Fish II, while enabling the crafts to be much more rugged, and significantly less costly to manufacture. Thus, such products can be manufactured for the consumer market, not just utilized as scientific experiments.
The advantages of external power input to assist human-power has been well known for over a century. Many people have offered for public sale vehicles that had battery assistance, as well as those with various configurations utilizing internal-combustion engines. One kind of wheeled vehicle, typically called a "Moped", uses an internal-combustion engine or electric motor to supply the majority of power; yet, offers a separate drive system to allow the operator to add additional power. To my knowledge, all of these vehicles used a separate drive mechanism for the human-powered, power input and the external energy supply.
For example, in U.S. Pat. No. 5,489,002, Glenn C. Streiff discloses a "solar-powered two-wheel vehicle with energy intensifying solar collector", which also utilizes a pair of rechargeable batteries to supply external power. The Streiff patent again discloses the use of chains and sprockets for both the pedal and the motor/generator system; and because it only had two wheels, vehicles using this concept will not be able to add energy, when the vehicle is stopped. Likewise, when using the motor/generator for "regenerative braking", that purpose will be defeated, if the operator tries to add energy to the system during times when the regenerative braking is taking place. The present invention is meant to remedy both of these limitations.